https://medium.com/@ryanhickman/augmented-reality-robotics-bb6db40ab754

Mars rovers and your smartphone have the same problem: figuring out where they are without GPS.

Whether you’re inside a mall, a deep parking garage, or an urban canyon, your cellphone’s GPS isn’t much use when it can’t see the sky. The same is true for robots on other planets where techniques such as Visual Odometry are used to track movement over time.